There are many known types of an upholstered sofa with a supporting structure provided with cushions forming the seat, the back and, in certain cases, also the side walls of the arms constructed in such a way that they can be converted to beds.
Generally, in order to use these sofas as single beds, it is necessary to remove the cushions so that it will be possible to use the supporting surface which is sprung or elastically yielding as a support for a mattress. A bed is finally prepared after the rearrangement of a mattress and is not convenient because of the presence of the fixed structure of the back along one side of the supporting surface and of the arms, also fixed, on the opposite ends of the said supporting surface. These fixed lateral structures create inconvenience for a user of the bed.
Sofas and armchairs which may be converted into single or double beds by turning over a movable part of the seat with respect to a fixed part in such a way as to obtain a horizontal surface usable for the superimposition of the mattress or mattresses are also known. These designs are of a complex and heavy structure, and almost always require the initial movement of the sofa away from the wall against which it is normally placed with more than a negligible amount of a physical effort.